In recent years, a network architecture of a centralized control type is proposed. As an example of the network architecture of the centralized control type, there is provided a technology called OpenFlow (refer to Patent Literature 1 and Non Patent Literatures 1 and 2).
<OpenFlow (OpenFlow)>
OpenFlow treats communication as end-to-end flow, and performs path control, malfunction recovery, load balancing, and optimization on a per flow basis. An OpenFlow switch (OpenFlow Switch: abbreviated as “OFS”) is specified in Non Patent Literature 2, for example. OpenFlow switch communicates with an OpenFlow controller (OpenFlow Controller: abbreviated as “OFC”) corresponding to a control apparatus, using a secure channel, for example. The OFS includes a flow table in which appropriate adding or rewriting is instructed by the OFC, and operates according to content of the flow table.
<OFS and Flow Table>
FIG. 6 is a diagram schematically illustrating a flow entry 120 of a flow table. In the flow table, a set of a matching rule (match field: Match Field) (header field) to be matched against a header of a packet received by the OFS, flow statistical information (Counters), actions (Actions) defining processing content is defined for each flow (refer to FIG. 6).
On reception of a packet, the OFS searches the flow table for an entry having a matching rule that matches header information of the received packet. When the entry that matches the received packet is found as a result of the search of the flow table, the OFS updates the flow statistical information (one or more Counters), and executes, for the received packet, processing content (e.g., transmission of the packet from a specified port, flooding of the packet, discarding of the packet, or the like) described in the field of actions (Actions) of the entry.
<Packet-In>
On the other hand, when the entry that matches the received packet is not found in the OFS as the result of the search, the OFS forwards the received packet (as a Packet In message) to the OFC through a secure channel and requests determination of a path for the packet based on information on a transmission source and a transmission destination of the received packet. The OFC calculates a path based on network topology information, generates a flow entry (in FIG. 6), and transmits a message for updating a flow table to each OFS on the calculated path. The OFS receives, from the OFC, information on the flow entry corresponding to the path for the packet determined by the OFC and updates a flow table. In this way, the OFS processes the received packet by using the information on the flow entry stored in the flow table as a processing rule.
[PTL 1]
    International Publication No. WO2008/095010[NPL 1]    Nick McKeown and seven other authors, “OpenFlow: Enabling Innovation in Campus Networks,” [online], [Searched on October 31, Heisei 24], Internet <URL: http://www.openflowswitch.org//documents/openflow-wp-latest.pdf>.[NPL 2]    “OpenFlow Switch Specification” Version 1.1.0 Implemented (Wire Protocol 0x02), [Searched on October 31, Heisei 24], Internet <URL: http://www.openflowswitch.org/documents/openflow-spec-v1.1.0. pdf>.